Recent images produced from the NASA Scatterometer (NSCAT)
are giving scientists new insights into the Antarctic ice sheet
and the Amazon rainforest after researchers devised ways of using
the ocean-monitoring instrument to study land and ice.

The scatterometer's primary function is to study winds over
the oceans, but a scientist at Brigham Young University (BYU),
Provo, Utah, has come up with a way of enhancing the resolution
of the instrument's radar backscatter to take a detailed look at
land and ice surfaces as well.

"A radar scatterometer measures the radar backscattering
cross-section of the Earth's surface. Measurements of the
backscatter over the ocean are used to infer the near-surface
wind speed and direction, but can also be used over land to study
ice and vegetation," said Dr. David Long, an NSCAT team member at
BYU. "Areas which reflect more microwaves are typically rougher
and appear brighter in the images than smoother areas which
reflect less. The electrical properties of the surface also
affect the image brightness. This is the first time we've been
able to provide rapid, global coverage that is both uniform and
accurate at this resolution."

The polar regions play a central role in regulating global
climate, and it is important to accurately record and monitor the
extent and surface conditions of the Earth's major ice masses,
according to Long. Scientists are using the Antarctic image to
understand the effects of the ice pack on the ocean and climate
systems. The image shows variations in the ice sheet, as well as
a "super-iceberg" that broke off the Thwaites ice tongue and is
now circulating in the sea-ice pack.

"Spaceborne radar remote sensors are uniquely well-suited
for mapping the polar regions since the radar can image the
surface through clouds and both day and night. Similarly,
radars are also useful for vegetation studies because different
vegetation types and densities have different radar responses,"
Long said. "Tropical rainforests are critical to the climatic
health of the Earth and are thought to contain half of all the
world's species."

The new NSCAT image shows the extent of the tropical
rainforest. The false color image is being used by scientists to
identify types of vegetation on the surface which allows them to
differentiate between areas of tropical rainforest and regions of
woodlands and savanna.

"This technique of using the scatterometer to study land and
ice is a great new application of this radar instrument. We can
get measurements of ice extent for use in
research and as an aid to shipping and we get them accurately and
frequently under all weather conditions," said Jim Graf, the
NSCAT Project Manger at JPL. "We can view large-scale vegetation
changes enabling us to track the processes of desertification and
deforestation. Data from the NSCAT instrument is extremely
versatile and can be used to measure short-term changes over the
oceans and long-term changes over the land and ice."

The scatterometer uses an array of stick-like antennas that
radiate microwave pulses in the Ku-band across broad regions of
the Earth's surface. A small fraction of the energy in the
radar pulses is reflected back and captured by NSCAT's antennas.
At any given time NSCAT's array of six dual beam antennas scans
two swaths of ocean or land --one on either side of the
satellite's near-polar, sun-synchronous 800-kilometer (500-mile)
orbit. Each swath is 600 kilometers (375 miles) wide. The
swaths are separated by a gap of about 350 kilometers (215 miles)
directly below the satellite, where no data collection is
possible.

The scatterometer makes 50-kilometer (30-mile) resolution
measurements of the wind over the oceans. This resolution is too
coarse for most land and ice studies, but through computer
processing of the data, Long is able to produce images with a
resolution of 8 kilometers (4.8 miles) or better. "This
resolution is still coarse when compared with photographs, but it
is nearly ideal for studying many land and ice processes," Long
concluded.

The NSCAT instrument was launched August 16, 1996, aboard
Japan's Advanced Earth Observing Satellite (ADEOS). ADEOS is an
international global change research mission of the National
Space Development Agency of Japan (NASDA), which includes
instruments from the United States, Japan and France and
investigators from many other countries. The satellite is a key
part of an international environmental research effort that
includes NASA's Mission to Planet Earth (MTPE) program, a long-
term, coordinated research effort to study the Earth as a global
environmental system. The goal of MTPE is to develop a better
scientific understanding of natural environmental changes and to
distinguish between natural and human-made changes and impacts.

The Jet Propulsion Laboratory developed, built and manages
the NSCAT instrument for NASA's Office of Mission to Planet
Earth, Washington, D.C.